Innocent Information

With the progress of modernization and development, cities are glittering with widely spread neon lights. These urban lights demonstrate the prosperity of cities but have gradually created light pollution to a varying extent, obscuring the stars in the night sky. Authorities have verified that the issue of light pollution is very serious across the globe and about 1/3 of the world’s populations cannot see the galaxy in a clear night sky while the lovers of starry sky photographing can do nothing but sigh. How to reduce the impact of light pollution on the photographed images and let us capture a beautiful starry sky? In the following text, the author will introduce a L-pro starry sky light pollution filter that can effectively increase the contrast of targets in the starry sky and eliminate the impact of surface light pollution to help starry sky photographers to easily capture a clear starry sky.

L-Pro light pollution filter parameters

Firstly, let us take a look at the spectrum measurement curves of L-pro filter. In the figure above, the orange line represents the wavelength corresponding to sodium (Na) lamp and mercury (Hg) lamp creating light pollution, the green line represents the wavelength of emission points corresponding to the line spectra such as emission nebula, planetary nebula and supernova remnants, the red line represents the wavelength of L-Pro filter and RGB color is within the range of 400-700mm. As shown in the figure, L-Pro filter filters the light pollution and other wave bands feature high transmittance, effectively increasing the contrast. In popular terms, L-Pro starry sky light pollution filter can effectively filter most manmade light pollution in cities, relatively increase the brightness of star lights by reducing the brightness of landscape lights, allow more time for exposure while effectively inhibiting the background light, and help starry sky photographers to capture more images of the starry sky.

L-Pro filter is coated on double sides in more than one hundred layers with the Japanese OPTORUN coating equipment, and coating technology independently developed by Optolong. The coating layers are firmer and tighter and the filter can operate properly even under inclement weather conditions. In addition, the frame of L-Pro filter is made of quality aviation-level aluminum material which has been subjected to CNC processing and anode oxidation. This material is resistant to corrosion, lightweight (50% lighter than titanium material), highly flexible and stable and has been widely used in various fields due to its good electromagnetic shielding performance and thermal conductivity. In addition, the surface of the frame has been dull polished to create a matte surface, which can help eliminate (absorb) stray lights, reduce diffuse reflection ad further improve imaging quality.

Measurement of photographing effects with L-Pro light pollution filterTechnical parameters only represent one side. As a mostly concerned aspect, how is the actual imaging performance of L-Pro light pollution filter? Let us take a look at the image of the great nebula M42 photographed by a professional photographer from Taiwan, Jerry Huang, with and without L-Pro filter:

It can be easily observed that in the image photographed with L-Pro starry sky light pollution filter, compared with the photo shot without L-Pro filter, the color and internal details of the great nebula M42 are clearer, the background is deeper, the profile of the scattering light halo is clearly legible, and the mystery and beauty of M42 are sufficiently highlighted. Let us look at the great nebula in Orion, M42, which is a diffuse nebula. This nebula is huge, bright and looks like a flying firebird and is therefore called “firebird nebula”.

Galaxy in summer:

The photographer Vincent Cheng said, “the difficult point for photographing the galaxy is that the composition of celestial bodies in the nebula is extremely complicated and due to the interference of background light (light pollution), the levels of the galaxy cannot be highlighted and then the beauty of galaxy stars cannot be fully shown. This time I have used L-Pro light pollution filter and I believe the effects of this filter are fairly good and the orange light pollution in the background has been effectively eliminated, the color of the starry sky is clear and distinct. L-Pro filter not only improves the quality of photos, but also reduces the physical environmental requirements for photographing starry sky and reduce the difficulty of image processing after photographing”.

From the comparison of photos shot with and without L-Pro filter, it can be seen that:

1. If the filter is used to photograph the galaxy, the filter will filter some lights and exposure time or light sensitivity needs to be increased to get the same exposure;2. The filter is suitable for use in the suburb or summit of hills to photograph the galaxy in summer and can effectively filter the light pollution while maintaining color balance;3. The filter is also suitable for use in conjunction with a modified camera in the suburb or summit of hills to photograph the galaxy and can effectively highlight the red details in celestial bodies;4. When the filter is used for photographing facing bright light sources, light spots affecting the image, such as halo, may be generated;5. The filter can filter light pollution but cannot improve the atmospheric visibility;6. L-Pro filter ensures better color balance and can be easily manipulated by new and senior photographers and allow for easy post processing.

Dimensions and specifications of the filter

In addition to 1.25” and 2” filters, which can be used on conventional astronomical telescopes, the Clip filter system designed by Optolong for mainstream cameras such as Canon, Nikon and Sony can reduce interferences with the filter which can cause wavelength shift on the wide angle end due to incident light and incident angle and result in non-uniform color of the images. Such filter system is suitable for super-wide angle lens.

Summary evaluation of L-Pro light pollution filter testing

In general, L-Pro light pollution filter is powerful for filtering light pollution and easy to use. Particularly, for new and amateur starry sky photographers, L-Pro light pollution filter allows you to capture satisfactory images of the starry sky without the need of doing any special effect processing of the photos. The layering, three-dimensional effect, clearness, image detail processing, color and quality of photos shot with L-Pro filer are greatly improved. The author is also a starry sky photographing lover and feels satisfactory with L-Pro filter.